1. Field of the Invention
The present invention relates to an expansion anchor to be set in a bore of a constructional component and including an anchor member having, at its end facing in a setting direction, an expansion region with a longitudinal slot open at its setting direction end, a guide region remote from the setting direction end of the anchor member, and a transition region located between the expansion and guide regions and having at least one opening, at least one radially projecting salient tab for preventing rotation of the anchor member during the setting process, with the expansion anchor further including an expanding member having a cone for expanding the expansion region of the anchor member.
2. Description of the Prior Act
Expansion anchors of a type described above are used in particular for securing an object to a constructional component formed, e.g., of concrete. Usually, a bore is formed in the constructional component for receiving the expansion anchor, in particular, the anchor member. The expanding cone expands the expansion region of the anchor member in the bore, securing the expansion anchor in the bore. In order to prevent rotation of the anchor member during the setting process, the anchor member is provided with at least one salient tab that is engageable in the bore wall. The transition region between the expansion and guide regions serves for obtaining a reliable anchoring in a constructional component formed with cavities, by permitting an axial displacement of the expansion region relative to the guide region. To insure this function, the transition region is provided with a plurality of openings. The openings lead to weakening of the anchoring member resulting in upsetting of the transition region under a certain axial pressure acting on the anchor member.
U.S. Pat. No. 4,720,224 discloses a one-piece expansion anchor having a transition region. The transition region is adjoined, at its setting direction end, by a slotted expansion region and at its opposite end, by a guide region. The transition region is provided with a plurality of openings. In the region of the longitudinal slot of the expansion region, there is provided a plurality of radially extending salient tabs which are engageable in the bore wall, preventing rotation of the anchor member during the setting process. The openings in the transition region allow for an axial displacement of the expansion region relative to the guide region. The openings, as discussed above, lead to an axial weakening of the transition region which results in upsetting of the transition region upon application of a certain axial pressure to the anchor member.
An advantage of the expansion anchor disclosed in U.S. Pat. No. 4,720,224 consists in formation of the anchor member as a one-piece part. This insures an economical manufacturing of the expansion anchor. In particular, an end assembly of the expansion anchor is simplified due to a reduced number of parts.
Drawbacks of the expansion anchor disclosed in U.S. Pat. No. 4,720,224 consist in difficulty of forming the salient tabs, which have to be pivoted outwardly relative to the circumference of the anchor member during manufacturing of the anchor member, and in that the salient tabs do not optimally fulfill their function of preventing the rotation of the anchor member during the setting process, which results in a partial rotation of the anchor member during setting.
Further, the known expansion anchor is practically unsuitable for an overhead work because this expansion anchor can be set only upon application of a significant force. Otherwise, it easily slides out of the bore upon expansion of the expansion region of the anchor.
An object of the present invention is to provide an expansion anchor with a transition region suitable for use in an overhead work.
Another object of the present invention is to provide an expansion anchor of the above-described type that would allow for a simplified formation of the salient tabs.
These and other objects of the present invention, which will become apparent hereinafter, are achieved by providing at least one opening in the transition region and by forming at least one salient tab in the region of the opening.
Advantageously, there are provided a plurality of openings in the transition region and a plurality of salient tabs formed in the regions of respective openings.
The provision of the salient tabs in the regions of the opening provides for economical manufacturing of the expansion anchor. The economical manufacturing results from the fact that both the openings and the tabs are formed in a single operational step. It is to be pointed out that when several openings are formed in the transition region, not all of them should have a tab.
Advantageously, the openings and the salient tabs have complementary shapes.
Advantageously, the salient tab pivots relative to the opening about an axis located in a plane extending perpendicular to a longitudinal axis of the expansion anchor, and has its free end extending in a direction opposite to the setting direction. The pivotability of the salient tabs and their extension in a direction opposite the setting direction insure an optimal hooking of the tabs in the bore wall.
In order to insure an optimal alignment of the salient tabs with respect to the bore wall, the transition region is formed with a diameter smaller than that of the expansion and transition regions. This makes it possible to increase the salient angle of the tabs in comparison with the angle of the salient tabs of the conventional expansion anchors. Further, the space between the reduced diameter of the transition region and the wall provides sufficient space for accommodating the eventual upsetting of the transition region.
Advantageously, the openings and, accordingly, the salient tabs have a triangular shape. This insures an optimal hooking of the tabs with their sharp tips in the bore wall.
The foregoing feature makes it possible to use the inventive expansion anchor in an overhead work. The anchor can be easily inserted into the bore but would not slide therefrom.
Advantageously, the anchor member is formed as a stamp-bent part of sheet metal.
In order to insure an economical manufacturing of the expansion anchor and, simultaneously, insure stability of the guide and expansion regions of the anchor member, according to a particularly preferred embodiment of the present invention, the wall thickness of the expansion and guide regions is doubled in comparison with the wall thickness of the transition region. In particular, when sheet metal bending-in-stamp process is used, preferable, the sheet metal can be folded once in the guide and expansion regions to obtain the desired thickness of these regions.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiment, when read with reference to the accompanying drawings.